It's possible to make money off of ads without collecting any personal data. Print publications and TV have been doing this for ages.
YouTube could target ads entirely based on the content of the video being watched. For example, if I'm watching a video of someone playing a video game, chances are that I'm interested in video games and they can show me ads for video games or gaming computers. They don't have to know anything about me or my viewing history to be able to do this. If I'm watching a video of a talk on functional programming, they can show me ads for high-end laptops. Same if I'm reading an article about programming on medium.com or some other blog site.
YouTube could target ads entirely based on the content of the video being watched. For example, if I'm watching a video of someone playing a video game, chances are that I'm interested in video games and they can show me ads for video games or gaming computers. They don't have to know anything about me or my viewing history to be able to do this. If I'm watching a video of a talk on functional programming, they can show me ads for high-end laptops. Same if I'm reading an article about programming on medium.com or some other blog site.